/* Smartphones (portrait and landscape) ----------- */

@media only screen 
and (min-width : 320px) 
and (max-width : 480px) {
    .main-container{
        width: 100%;
        height: 100px;
        border: 1px solid orange;
    }

    .main-container .header{
        width: 100%;
        height: 100px;
        border: 1px solid olive;
    }
}

@media only screen 
and (min-device-width : 320px) 
and (max-device-width : 480px) {
    .main-container{
        width: 100%;
        height: 100px;
        border: 1px solid blue;
    }

    .main-container .header{
        width: 100%;
        height: 100px;
        border: 1px solid red;
    }
}

/* Smartphones (landscape) ----------- */
@media only screen 
and (min-width : 321px) {
    /* Styles */
}

/* Smartphones (portrait) ----------- */
@media only screen 
and (max-width : 320px) {
    /* Styles */
}

/* iPads (portrait and landscape) ----------- */
@media only screen 
and (min-device-width : 768px) 
and (max-device-width : 1024px) {
    /* Styles */
}

/* iPads (landscape) ----------- */
@media only screen 
and (min-device-width : 768px) 
and (max-device-width : 1024px) 
and (orientation : landscape) {
    /* Styles */
}

/* iPads (portrait) ----------- */
@media only screen 
and (min-device-width : 768px) 
and (max-device-width : 1024px) 
and (orientation : portrait) {
    /* Styles */
}

/* Desktops and laptops ----------- */
@media only screen 
and (min-width : 1224px) {

    .main-container{
        width: 100%;
        height: 100px;
        border: 1px solid #ccc;
    }

    .main-container .header{
        width: 100%;
        height: 100px;
        border: 1px solid #ccc;
    }
}

/* Large screens ----------- */
@media only screen 
and (min-width : 1824px) {
    /* Styles */
}

/* iPhone 4 ----------- */
@media
only screen and (-webkit-min-device-pixel-ratio : 1.5),
only screen and (min-device-pixel-ratio : 1.5) {
    /* Styles */
}